地震作用下钢筋混凝土桥墩有效截面抗弯刚度

Flexural stiffness of equivalent section of RC piers subjected to earthquakes

为了实现常规桥梁的基于位移的简化抗震设计,有必要简化钢筋混凝土(RC)桥墩有效截面抗弯刚度的计算.将RC桥墩有效截面抗弯刚度与毛截面抗弯刚度的比值定义为有效截面抗弯刚度修正系数Reff,采用纤维单元程序UCFyber对我国常用的矩形、圆形以及矩形带倒角等截面形式的RC桥墩的Reff进行了模拟计算,曲线拟合得到Reff的简化计算公式,最后采用Opensees程序分析了多个RC桥墩的地震位移反应,对Reff简化计算公式的精度进行了检验,并确定了其应用范围.结果表明:RC桥墩的有效截面抗弯刚度修正系数Reff主要与截面轴压比和截面纵筋配筋率有关,受其他因素的影响较小;截面轴压比和截面纵筋配筋率越大,Reff越大;对于高宽比大于3.0的相对细长RC桥墩,采用Reff简化计算公式对应的RC桥墩有效截面抗弯刚度,能够获得合理的地震位移反应.

It is necessary to simplify the calculation of the flexural stiffness of the equivalent section of reinforced concrete(RC) piers to provide a basis for the simplified displacement-based seismic design of ordinary RC bridges.The ratio of RC piers' flexural stiffness of the equivalent section to that of the gross section is defined as the correction factor of flexural stiffness of the equivalent section(Reff).Then the fiber element procedure UCFyber is used to calculate Reff of rectangular sections,circular sections,and other rectangular sections with chamfer,which are universal in Chinese RC piers,and the results are curve-fitted to obtain the formula of Reff.Finally,the Opensees software is used to analyze several RC piers' seismic displacement responses to check the accuracy of the formula of Reff and identify its application range.The results show that Reff mainly depends on the axial compression ratio of the section and the area ratio of longitudinal reinforcement and the influence of other parameters can be neglected.Furthermore,Reff increases with the increase of the axial compression ratio of section and the area ratio of longitudinal reinforcement.As for the relatively slender RC piers with the height-width ratio of more than 3.0,rational seismic displacement response can be obtained by using the flexural stiffness of the equivalent section calculated by the formula of Reff.